Answer:
Undefined
Explanation:
Slope is equal to the change in y over the change in x.
m = (y₂ - y₁) / (x₂ - x₁)
Let your points (5, 6) be (x₁, y₁) and (5,-8) be (x₂, y₂). Therefore you have
m = (-8 - 6) / (5 - 5) = -14 / 0
Dividing by zero will lead you to have an undefined slope